Video conferencing or video teleconferencing provides a way for parties at different locations to see and hear each other while holding a conference. Video conferencing has been demonstrated since the advent of the television, but did not become commercially viable until the 1980's with the development of the Integrated Services Digital Network (ISDN). ISDN is a set of communications standards that allow for transmission of voice video and data over the copper wires of the Public Switched Telephone Network (PSTN). As the Internet has grown, video conferencing tools have migrated toward packet switched Internet Protocol (IP) based networks.
In IP based video conferencing, a conference bridge may be used to aggregate and distribute data. For example, when a conference has five parties at five different locations, each of the locations streams audio and video to the conference bridge. The conference bridge then streams one of the video streams, usually associated with the lecturer or primary speaker, to all of the locations such that all participants may see the speaker, e.g., using IP unicast video streams that are streamed to each individual participant. Audio, on the other hand, may be mixed by the conference bridge before being streamed to the parties. In one example, the primary speaker's voice along with the voice of one or two other conferees may be mixed before being streamed so that all participants can hear a conversation. The audio from any other conference participants (conferees) is filtered out, thereby reducing background noise.